Justin Blanton perfectly sums up my biggest fear:
I kind of can’t wrap my head around how thin it is—just 8.8mm (that’s thinner than an iPhone 4!). Whether this helps or hurts its ability to be comfortably held over a protracted session remains to be seen; my guess is that, even with the lighter weight (1.33 pounds vs. 1.5 pounds), it will make it more difficult to hold, especially since it still has the same slippery aluminum back. I really wish they’d rubberize these things.”
I don’t agree with rubberizing it, I think that has a poor tactile feel and is prone to looking dirty. I can say though that I worry that this will fatigue your hands if you are holding it to read while laying in bed — a thin device like this requires a better grip to support the weight than a similar, but thicker, device would.
Justin has a great look at the iPad from one of the few people I know that sold theirs because they couldn’t find a use for it.